Paper manufacture



June 5, 19351. J TRAQUAIR' 1,961,405

PAPER MANUFACTURE Filed Aug. 17, 1928 3 Sheets-Sheet l 20%, j /NVN TORWM BY hwM d ATTORNEY June 5, 1934. J. TRAQUAIR 1,961,405

PAPER MANUFACTURE Fi led Au 17, 1928 s sheets-sheet 2 INVENTQR A TTORNEY3 June 5, 1934. I J. TRAQUAIR I 1,961,405

PAPER MANUFACTURE Filed Aug. '7, 1928 3 Sheets-Sheet 5 2 h J IIIT OI y;I a t\ Q c N Q; i I N I a I INVENTOR yfim y m BY )Wm wr/AA/K M 0 ATTORNE Y5 Patented June 5, 1934 UNITED STATES PATENT OFFICE PAPERMANUFACTURE John Traquair, Chillicothe, Ohio, assignor to The MeadResearch Engineering Company,

This invention relates to the manufacture of paper, and particularly tothe manufacture of various classes of board, such as container board,corrugatedboard, egg case fillers and the like, and to the manufactureof various grades of wrapping paper.

One of the principal objects of the invention is to provide a superiormethod of, and apparatus for, treating raw fibrous materials such asvarious classes of wood, straw, cereal grasses, cane, bamboo, reeds andthe like in the manufacture of paper.

Another object of the invention is to provide such a method andapparatus which function to produce a larger yieldof better gradepaperforming stock from a given quantity of raw fibrous material and ata smaller cost.

Still another object of the invention is to provide such a method andapparatus which function continuously and are self-contained, whicheliminate digestion or cooking, and which admit of recovery of thechemicals used to eliminate waste and stream pollution.

Other objects and advantages of the invention will be apparent from thefollowing de-, scription, from the drawings and appended claims. I

In the drawings in which like characters of reference designate likeparts throughout the several views therof, 4

Fig. 1 is a side elevational view, somewhat diagrammatic, of a portionof apparatus adapted particularly for the treatment of straw, cerealgrasses and the like, constructed in accordance with this invention andadapted for carrying out the method of this invention;

Fig. 2 is a side elevational view, somewhat diagrammatic, of anotherportion of the apparatus, Figs. 1 and 2 .when placed end to enddisclosing the complete apparatus;

Fig. 3 is a side elevational view, somewhat diagrammatic, of apparatusconstructed particularly for the treatment of wood in accordance withthis invention; and

Fig. 4 is a side elevational view, somewhat diagrammatic, of a modifiedform of apparatus constructed particularly for the treatment of wood inaccordance with this invention.

The method of the present invention is adapted for the treatment ofvarious classes of wood, and particularly various 'types of waste woodas representing an economical source of supply of raw material. Forexample, the method is applicable to the treatment of cull lumber,shavings, waste wood from furniture pulp, and which impart to theresulting strawand box factories, sawmill waste, leached chips fromtannin extract mills, and the like. The

process is more especially applicable to the'various deciduous ornon-resinous broad-leaf woods, also called the hard woods, such aschestnut, gum, poplar, birch and the like. The methods heretoforegenerally used in this country for the pulping of' wood consist incooking the wood by boiling under pressure with strong cooking liquor,such as caustic soda, bisulfites, or sodium sulfate, as exemplified inthe well known soda, sulfite and kraft processes. In all these processes where the wood is. subjected to cooking treatment, the yield isquite low, seldom being over 50% and generally around 40%. Furthermore,the cellulose fibers are deleteriously affected by the cookingtreatment, thereby reducing their strength.

The method of the present invention is also adapted for the treatment ofstraw, cereal grasses, cane, bambo, reeds and the like. The term strawas hereinafter used is not meant to be a limitation, but merely asdesignating all such analogous materials. The method heretoforegenerally used in this country in the manufacture of strawboard consistsin cooking the straw by boiling it in strong lime solution. underpressure. The strawboard which is thus produced has a limited utilitybecause of its poor color and because it is hard and brittle and oflimited strength. In addition the lime appears to combine with some ofthe constituents present in the straw forming lime compounds which I cannot be efiectively removed from the straw 00 board a disagreeable odor.Furthermore, chemicals used in this method of treatment do not adaptthemselves to recovery and consequently a large amount of exhaustedchemicals and straw material are lost in the process. The waste materialand chemicals are customarily allowed to fiow into nearby streams, theresulting stream pollution being so objectionable that legislatures inmany states have passed measures against such practices. I

According to the present, invention a-method for the treatment of wood,straw and the like, in the making of paper forming stock is providedwhich produces a, finished paper or board free from objectionable odor,which has greater strength than paper or board made. from the same rawmaterials by other generally used 'methods of treatment, which utilizeschemicals which may be recovered and thus used over and over to providea continuous self-contained process without the production of streampolluting waste, and which gives an unusually high yield of better-gradepaper-forming stock.

In accordance with this method, the raw fibrous material is firstsub-divided to suitable size, and is then mechanically disintegrated inthe presence of an alkaline liquor. Sub-divided fibrous material when inan alkaline condition is found to possess characteristics of softnessand unusual ease of refining to a flexible pulp. With mechanicaldisintegration in the presence of an alkaline liquor, only relativelysmall percentages of the fibrous material are dissolved or lost in theprocess, a-substantial portion of lignins and pentosans remaining in thestock, increasing the yield as well as functioning as a natural size. Asrepresenting a suitable and preferred form of disintegrator, a rod millis shown and described herein. However, it is to be understood'that' anysuitable disintegrating mill can be used, which functions to subject theraw material to a pounding, rubbing or shredding ac tion, to sub-dividethe material into fibers and to hydratethese fibers and adapt them forformation of a suitable sheet on the forming machine. For example, adisintegrating mill of the swing-hammer type may be used. Thedisintegrated pulp is then filtered and washed, and is then furtherreduced in a refiner, such as a Jordan, when it is ready to be passed tothe paper machine.

-When straw or fibrous grasses and the like are being treated it isfound preferable to first subject such materials to a steeping action inan alkaline liquor to wilt and soften them. Such a steeping action maybe applied to wood with good results. This -is accomplished by immersingthe raw fibrous material in alkaline liquor of controlledcharacteristics where it is steeped at a controlled temperature belowthe boiling point of such liquor and at substantially atmosphericpressurer The steeping liquor which is caustic in character, is soconstituted that the temperature and pressure at which the steeping iscarried on effects a primarysoftening of the bonding material holdingthe cellulose fibers together without a material destruction of theshape or appearance of the raw fibrous material and without anydeleterious: effect upon the cellulose fibers, so that by mechanicaltreatment the fibers may be readily separated or the raw materialdisintegrated. The steeped fibrousmaterial is removed from the steepingliquor and allowed to drain until it contains a controlled amount ofretained liquor still having substantial causticity when it is thensubjected to mechanical disintegration, as'in' a rod mill, in thepresence of retained liquor of substantial causticity.

In the treatment of wood it is found that very satisfactory results maybe secured by adding controlled and proportionate amounts of wood chipsand caustic liquor directly to a rod mill where the chips aremechanically disintegrated in the presence of caustic liquor. Theamounts of caustic liquor added is preferably controlled so that theliquor is absorbed by the wood chips during the disintegration. It isfound that if the partially disintegrated chips are allowed to stand inthe presence of their absorbed alkaline liquor for a period of time,such as for about 12 to 24 hours, they defiber more readily than if theyare run directly through the apparatus. Very satisfactory results may besecured in this manner by using two or more rod mills in sistency,preferably at about 10% or under, is

then passed through a second rod mill.

The alkaline licmir, either added in the steeper or added directly 0 theraw material entering the rod mill, may

perature of the treatment are inter-dependent, the hotter the liquor theless time required for the proper softening of the raw material. Verysuitable results have been obtained by maintaining the liquor at atemperature slightly below the boiling point, about -C., in order toprevent objectionable steam formation which would escape freely into thebuilding containing the open steeping tanks or. open-ended rod mills. Bythis method the yield of finished stock is usually in excess of 70% ofthe original raw materials, and yields as high as 90% have beenobtained.

I Referring to Figs. 1 and 2 in the drawings, apparatus constituting apreferred embodiment for the treatment of straw, fibrous grasses and thelike is illustrated. Bales of straw as indicated at 10 are placedupon anendless conveyor 11 which is adapted to be driven at a suitable speed byany suitable mechanism not illustrated. After being placed 'upon theconveyor belt 11 the bales 10 are brokenppen before being fed into theduster mechanism 13. The duster mechanism may be of the conventionaltype used in the industry for dusting old paper stock and. the like, and'needs no further illustration. Toothed rolls 14 are provided forpulling the straw apart and feeding it into the duster and for suitablysub-dividing it. The loose straw feeds through the discharge .chute 15directly into the feeding hopper 16 of the steeping tank 1'7. A spraypipe 18 suitably perforated on the under side is adaptedto spray causticliquor upon the straw as it feeds into the hopper 16 to thereby wilt thestraw and facilitate its pasage into the tank 17. The spray pipe 18 isconnected by pipe 19 with a suitable source (not shown) of fresh causticliquor which may come directly from a recovery plant for the spentliquor.

Any suitable construction of steeping tank, such as that disclosed inthe co-pending'application of John Traquair, SerialNo. 160,096, filedJanuary 10, 1927, issued as Patent No. 1,843,464; dated Feb. 2, 1932 maybe used. As shown, the tank comprises an elongated prefer ablycylindrical casing 20 which is normally kept substantially filled withsteeping liquor. Passing through the inlet end of the tank is a shaft eeither hot or cold. I It is found that the time of treatment and thetem- 23 which carries within the tank suitable means able source ofpower (not shown) in order to rotate the screw 24. l I

The outlet end of the steeping tank 17 as indicated at 2'7 is open topermit the free flow of steeping material through this end. A dischargechamber 28 is formed at this end of the tank by an extension of thecasing. Supported on a roll 29 which is journaled in opposite sides ofthe chamber 28 and running thereover is an endless elevator indicated at30. The elevator is provided with a plurality of wire buckets 31, eachof which is preferably constructed somewhat in the form of a pitchforkhaving a plurality of curved prongs. A suitable supporting and enclosingstructure 32 is provided for the upper end of the elevator and a secondroll 33 journaled in this supporting structure carries the elevator atthis end. Either of the rolls 33 or 29 may be positively driven by anysuitable mechanism (not shown) in order to elevate the steeped materialfrom thesteeping tank 1''! and discharge it through the chute .35. Asthe pass above the liquid level, the liquor contained therein drainsrapidly back into the steeping tank. The height of the elevator is soproportioned that a large percentage of the steeping liquor is thusreturned to the steeping tank, the straw passing through the chute 35preferably carrying from 5 to 6 parts of liquor to one part of straw. H

The steeping liquor is preferably maintained hot, but below the boilingpoint, although satisfactory results may be obtained by using coldliquor andincreasing the time of steeping. Very suitable results havebeen obtained by maintaining the steeping liquor at a temperature ofabout 90 or 95 C. and so proportioning the speed of the screw conveyor24 that the straw is allowed to steep for approximately one-half to onehour. It is found that quite dilute steeping liquor functionssatisfactorily, and satisfactory results are obtained by steeping in asdilute liquor as 1% NaOH. The concentration may be varied between 1% and6% with satisfactory results, but increasing the concentration above 6%does not appear to give advantages sufficient to make the increasedconcentration desirable.

Any suitable means may be employed in maintaining the steeping liquor atthe proper temperature where hot liquor is used, such as theconstruction disclosed in applicants co-pending application referred toabove. As shown, a false perforated bottom 36 ispreferably provided forthe steeping tank, the bottom of the shell 20 of the steeping tank beinginclined below this false bottom from the ends of the tank downwardlytoward the center as indicated at 37 to provide a. liquor removingchamber 38. "Liquor may be removed from this chamber through a pipe 39and passed through suitable filtering and heat- 4 .ing apparatus (notshown) and then returned to the steeping tank to maintain thetemperature. Further, the liquor introduced through the pipe 18 may beheated to assist in maintaining the temperature. A large excess ofliquor is preferably used in the steeper so that the straw will befloated along with the liquor. Very satisfactory'results are obtainedwhen as much as twenty parts of liquor are used to one part of straw, atwhich proportion the strawmoves easily. The causticity of the liquor is"takes place rapidly within the steeper.

suitable conventional construction. buckets or forks conveying thesteeped strawfrom the steeping tank retains a portion of the liquor asabove described, which liquor still has substantial causticity,preferably around 30% of the original active caustic content or over.That is to say,less' than of fresh caustic added has reacted with thefibrous material so that the liquor retained in the removed straw stillcontains about 30% or over of active caustic content. With this method,the total caustic consumption is generally maintained as low as 5% to10% on the dry weight of .the fibrous material, the major portion ofwhich reaction Very satisfactory re ults are obtained by adding asuflicientexcess fif active caustic liquor to insure that the liquoretained in the steeped material has substantial causticity of the orderabove mentioned.

The steeped fibrous material with retained caustic liquor is introducedinto the inlet end 40 of a rod mill 41. The rod mill may be of any Asillustrated, the mill is of the Hardinge type having standards 47, thebearings receiving and rotatably supporting the hollow trunnions. Withinthe casing 42 are a plurality of metal rods 48. On the exterior of theshell 42 is an annular ring gear 49 which is driven from any suitablesource of power (notshown) in order to rotate the casing 42. As thecasing rotates, the tumbling and cascadingof the. rods 48 within thecasing effects a pounding, rubbing and shredding treatment of thefibrous material passing into the rod mill which effectivelydisintegrates or defibers this material. It is found that the uncookedfibrous material in the presence of the caustic liquor, or in a fairlyalkaline condition,

possesses characteristics which permit effective mechanicaldisintegration without the consumption of excessive power. Satisfactoryresults are obtained by controlling the feed to the rod mill so that aneifective time of treatment of provided with removable covers, adjacentthe discharge end. The disintegrated pulp may therefore be dischargedthrough the hollow trunnion 45 or" through the ports 50 or 51', orthrough several of these sets of ports, depending upon the charatcer ofthe material being treated. When pulp of high consistency, such that itwill not readily fiow through the mill is being treated, the peripheraldischarge ports 51 or the ports 50 in theconical end wall are generallyused. When pulp of lower consistency such that it will flow is beingtreated, the ports 50 and 51 are generally closed by the removablecovers and the disintegrated material is discharged through the hollowtrunnion 45.

As shown, the material discharged from the rod mill is passed eitherthrough the chute 55 or the discharge opening 56 into a pit or chamber57 forming a stock chest. Passing transversely through the chamber 5'7is a shaft 58,- which extends through stufling boxes to theexdrivingpulley or gear 87.

terior of the pit and is provided with exterior bearings 59 and 60.Fastened ,to the shaft 58 within the chest 57 are a plurality ofagitators or mixing arms 61, shown to be three in number. Theseagitators 61 may be of any suitable construction, and are provided tostir up and mix the stock within the chest 57. As shown each Q adischarge pipe 65 within which is connected a pump 66, illustrated as ofthe centrifugal type, driven by an electric motor 67. The discharge endof the pipe 65 feeds the stock into the central compartment of aconventional head box 68 which is provided with an overflow partition 69by which the excess of stock pumped thereto may be discharged into thereturn pipe of the stock may be discharged through a chute 73 into aconventional mixing. box 74. The mixing box 74 is provided with aplurality of staggered bafiles indicated at 75 to thoroughly mix thestock passing therethrough. The mixing box '74 d'scharges into a pipe 76which feeds into an open tank 77.

Rotatably mounted and dipping in the stock within the tank 7'7 is arotary vacuum filter 80, which filter may be of any conventionalconstruction, for example of the type known commercially as the Oliverfilter, such, filters being well known in the art and so notparticularly illustrated herein. This filter 80 comprises a perforatedrotary screen divided into compart ments of definite suction areas. Thescreen ips into the stock Within the 'tank 77, the suction causing thefibrous material to accumulate on the surface of the screen; As thescreen rotates carrying the filtered defibered material above the liquidlevel w'thin the tank, sprays of "the liquor being at th's timesubstantially spent of its active caustic content and so may be termedblack l'quor.- As the filter continues to rotate, the material which hasthus been washed arrives at an area which is not subject to suetion, andat this point a flexible scraper member (not shown) carried by the s'deof the tank '77 scrapes this material from the filter, causing it withthe assistance of suitably directed sprays to slide down the scrapermember over the edge of the tank 77 into a chute 82 which discharges at83 into a stock chest 84 provided with an ag'tating shaft 85 havingagitators 86 and a As the fibrous material accumulates upon the screenof the rotary vacuum filter 80, the black liquor is sucked through intothe interior of the filter, andthen the remaining black liquor in thefibrous 'material is washed out by the sprays directed upon the fibrousmaterial, so that the black lquor is substantiallyall removed from thefibrous stock. Preferably controlled amounts of wash-water are added tothe fibrous stock on the filter, so that the black liquor issubstantially all washed out, the washing ater taking its place, but sothat unnecessary dilution of the black liquor is avoided. Th lack liquorsucked from the fibrous mater al to the interior of the filter 80 passesby the pipe 90 to the vacuum tank 91 provided in connection with thevacuum filter. This vacuum tank 91 is also of conventional construction,such as is used in connection with rotary vacuum filters of thischaracter, the vacnum tank being provided with a vacuum pump 92 forproducing the necessary suction within the rotary vacuum filter. Forwithdrawing the black liquor from the vacuum tank'91 against suctionexisting therein, a pipe 93 is tapped into the bottom of k the vacuumtank 91, and a centrifugal pump 94 operated by a motor 95 is positionedwithin the pipe 93. The pump 94 discharges into a pipe 96 which in turndischarges into the central compartment of a second head box 98.

The head box 98 is provided with an overflow partition 99 whereby theexcess of black liquor is discharged into a pipe 100, which in turndischarges into the stock chest 57. The black liquor thus removed fromthe fibrous stock in the rotary vacuum filter is returned to the chest57 to make down or dilute the stock discharged into thechest from therod mill, the stock being -made down at this point to a consistency suchthat it will readily fiow and can be pumped, preferably about 3%-to 5%.The stock is further made down before it passes to the rotary vacuumfilter by means of water or dilution liquor added at the head box 68from a pipe 102, so that the consistency of stock passed to the Oliverfilter is about 1%.

The head box 98 is also provided with a second partition having asliding gate 106 with a controlled opening or weir. In this mannercontrolled amounts of the black liquor pumped to the head box 98 aredischarged into the pipe 107 which leads to a recovery plant (not shown)which may be of entirely conventional form such as used in the recoveryof black liquor formed in the digesters in the manufacture of soda pulp.The steps in the recoveryor regeneration of the liquor are well'known,and consist essentially of evaporation of the liquor, burning of theresidue to black ash, the lixiviation of the black ash, and thecausticization of the extracted liquor. From the recovery plant, freshcaustic liquor may be supplied through a conventional heater (not shown)to the spray pipe 19. Thus a self-contained process for the manufactureof paper-forming stock from raw fibrous materials is provided, in whichthe chemicals used can be recovered so that there is little loss ofchemicals in the-process, and stream pollution is entirely avoided.

The stock chest 84 is provided with an outlet pipe 110 through which thestock is adapted to be pumped by a centrifugal pump 111 driven by amotor 112 through pipe 113 to a gravity feed head box 114. The head box114 is provided with a discharge pipe 115 which feeds into the inlet end116 of a conventional refiner; illustrated as a Jordan 117. The Jordanmay be of entirely conventional construction and so is not moreparticularly illustrated herein, and comprises a conical or tapered plughaving exterior knives driven by a motor 120 through a flexible coupling121, and a surrounding similarly shaped conical casing 122 havinginterior knives cooperating with the exterior knives on the plug. Thepulped fibrous material passing its character controlled so that it isin a satisfactory condition to be passed to a forming machine where itis made into board, or wrapping paper, or the like. The Jordan isprovided with a hand control 123 whereby the inner plug may be regulatedwith reference to the stationary casing 122 to control the refiningaction and there fore control the final characteristics of the pulp. Inthis manner, satisfactory pulp for formation into a good grade of boardor wrapping paper may be prepared directly by mechanical disintegrationwithout cooking. The pulp is discharged from the Jordan through a pipe124 which leads the refined pulp to a suitable stock chest or head boxof the paper-forming machine (not shown).

In Fig. 3 is illustrated a preferred embodiment of apparatus adaptedparticularly for the treatment of wood. A hog or chip breaker isillustrated at 130, this being of entirely conventional construction asused in the industry for breaking up logs or pieces of wood into chipsof a size such as is used for boiler fuel for example. The chips aredischarged through a chute 131 into a chip storage 132, which may be ofsilo construction comprising a cylindrical container having an openupper end 133 and a lower inclined or conical end 134 with a dischargeopening 135 feeding into a conveyor 136.

The conveyor 136 may be of any suitable construction, being illustratedherein as a screw conveyor having a single shaft 138 driven from apulley or gear 139 and carrying a helical screw 140. Intermediate theintake and discharge of the conveyor 136 is positioned an alkalineliquor supply pipe 142 controlled by a valve 143. The

discharge end of the conveyor 136 is positioned within the hollow inlettrunnion 145 of a rod mill 41', similar to the rod mill above described.

The speed of the screw conveyor 140 and the supply of caustic liquorcontrolledby the valve 143 are so coordinated thatthe raw chips and thecaustic liquor are admixed in controlled and proportionate amounts priorto the introduction of the mixed mass into' the rod mill 41'. It isfound preferable from the standpoint of economy and satisfactoryoperation to control the addition of caustic liquor to an amount whichcan be absorbed by the disintegrated material during the rod milling.Very satisfactory results have been secured where subjected totreatment'in the rod mill for about ten to twenty minutes. Where theliquor is added directly to the chips entering the rod mill withoutsteeping, a more concentrated liquor than that used in the steeper ispreferably us'ed. Very satisfactory results are secured with a liquorcontaining from about 3% NaOH to 10% NaOH, although more dilute liquormay be used with .an increase in the time of treatment.

The partially disintegrated chips and admixed liquor, which at this timestill retains a substantial amount of causticity, are discharged throughthe discharge trunnion 146 into an elevator 147 which may be of similarconstruction to that above described, except that where chips are beinghandled ordinary perforated buckets 148 are provided instead'of thepitchfork type of buckets. Where chips at high consistency are beingtreated, the disintegrated material is usually discharged. throughperipheral ports 51 onto a chute 149 which in turn feeds into theelevator 147. The elevator 147 is arranged to discharge through chute150 into a chip storage 151 which may be of silo construction similar tothe chip storage 132. The size and capacity of the'chip storage 151 isso proportioned" to plant operation, that the chips with absorbedcaustic liquor may be allowed to stand therein for a substantial periodof time suchas about 12 to 24 hours. This storageperiod is thusaccommodated during the] continuous operation of the plant and as thechips pass from the upperend to the lower end of the chip storage 151.It-is found that byallowing the disintegrated chips with absorbedcaustic liquor to stand for this-period, a further reaction between theliquor andthe fibrous material takes place with additional softening ofthe material, and it is more readily'and completely disintegrated by asecond-disintegrating treatment.

The fibrous material with its absorbed liquor is discharged through thescrew conveyor 155 into a second rod mill 156', similar to the rod mill41'. At this point the fibrous material 'is preferably made down to alower consistency in order to prevent the wadding up of the pulp and toprovide for a more eifective disintegration and hydration of the fibers.For this purpose a head box 98 similar in construction to thatpreviously described is provided. Black liquor removed from previouslytreated stock by a rotary vacuum filter as above described is introducedthrough pipe 96 into the central' compartment of the head box 98, and anoverflow partition 99 isv provided therein so that controlled amounts ofliquor may be added through pipe 157 into the screw conveyor 155 to makedown the pulp passing into the rod mill 156. Very satisfactory resultshave been secured where the pulp is made down to about 10% consistencyor under, and the mixed mass rod milled for about ten to twenty minutes.

The head box 98 is also provided with a second partition 105 controlledby a sliding gate 106' having an overflow opening or weir through whichcontrolled amounts of black liquor may pass into a pipe 107 leading torecovery. The pulped fibrous material isdischarged from the rod mill 156into chute 160 which empties into a stock chest 57'.. At this point, thestock is further made down to a consistency such that it will fiow, andis then pumped to a rotary'vacuum filter where it is filtered andwashed, and is then further refined in the manner above described inconnection with Figs. 1 and 2, the remainder of the apparatus beingsimilar to that shown therein and so not illustrated in this figure.

In Fig. 4 is disclosed a somewhat modified form of apparatusparticularly adapted for the treatment of wood. A. chip storage 132" fedby valve 143" supplies a controlled and proportionate quantity ofalkaline liquor. The conveyor discharges the mixed mass into the inletor feedconnection with Fig. 1.

ing hopper 170 of a steeping tank 17" similarin construction and.operation to that described in The chips after steeping and softeningare removed by the bucket elevator 147", the chips draining rapidly toabout 1% to 2 parts of liquor to one of chips., The

chips with absorbed liquor of substantial causticity are discharged intoa chip storage 172 which is also of the silo construction having an openupper end and an inclined lower end feeding into a conveyor 173discharging into a rod mill 41". The chip storage 172 is providedbetween the steeper and the rod mill in order to permit the steeper androd mill to operate at varying rates and to give flexibility to theopera-, tion. A pipe 174 controlled by a valve 1'15 is provided, so thatcontrolled quantities of liquor may be introduced into the conveyor 1'73to vary the consistency of the material fed to the rod mill 41".Generally, where the chips have been subjected to an initial steepingthe consistency is preferably made down to about 10% or under before themass is introduced into the rod null 41'', and a single rod-millingtreatment is ordinarily satisfactory. However, if desired, thedisintegrated mass discharged from the rod mill charged into a secondrod mill as disclosed in Fig. 3. The remainder of the process, includingfiltering, washing and refining, is the same as that described above andso is not further illustrated herein.

Instead of filtering and removing the alkaline liquor from thedisentegrated pulp prior to refining, the mass discharged from the rodmill may be run directly into the refiner, such as a Jordan, so that itis refined when in an alkaline condition. This gives somewhat higherstrength values under certain conditions of treatment and with certaintypes of pulp. Where rapid penetration of alkaline liquor into thefibrous ma-' teriaLis desired, very satisfactory results are secured bypassing the dry raw material, such as the chips, into a disintegratingmill, such as arod mill, which serves to crush and flatten the it is tobe understood that other alkaline liquors may be used, such'as potassiumhydroxide, sodium carbonate, and the like. I

The pulpproduced by this method and the apparatus disclosed is found tobe highly superior to the usual straw pulp made with a lime cook,

for example, and board manufactured from the pulp in accordance withthis method is found to be more than twice as strong as the conventionalstrawboard.

-While the method herein described, and the form of .apparatus forcarrying this method into effect, constitute'preferred' embodiments ofthe invention, it is to be understood that the invention is not limitedto this precise method and form of apparatus, and that changes may bemade an either without departing from the scope of the invention whichis defined in the appended claims. 1 I

What is claimed-is:

1. In the preparation of paper-forming stock, the method which comprisesintroducing unpulped fibrous material into a mechanical disintegrator,simultaneously introducing an alka line liquor into said mechanicaldisintegrator, passing the. fibrous material through said disintegratorwhile subjecting it to pounding treatment of impact elements tofacilitate impregnation of the fibrous material with the alkalineliquor, discharging the impregnated fibrous mais being fed thereto, andthen subjecting the impregnated fibrous material to further mechanicaldisintegration in the presence of absorbed alkaline liquor.

2. In thepreparation of paper-forming stock, the method which comprisesintroducing raw uncooked fibrous material into a mechanicaldisintegrator, simultaneously introducing an alkaline liquor into saidmechanical disintegrator, passing the fibrous materialthrough saiddisintegrator while subjecting it to pounding treatment of impactelements to facilitate impregnation of the fibrous-material with thealkaline liquor, discharging the impregnated fibrous material from thedisintegrator as fresh material is being fed thereto, and thensubjecting the impregnated fibrous material to a repetition of thepounding treatment of impact elements in the presence of absorbedalkaline liquor.

3. In the preparation of paper-forming stock, the method which comprisesintroducing raw wood chips which have not been previously- 4. In .thepreparation of paper-forming stock,

the method which comprises introducing unpulped fibrous material into amechanical dis integrator, simultaneously introducing an alkaline liquorinto saidmechanical disintegrator,

passing the fibrous material through said disintegrator while subjectingit to pounding treatment of impact elements to facilitate impreg nationof the fibrous material with the alkaline liquor, discharging theimpregnated fibrous material from the disintegrator as fresh material isfed thereto, allowing the impregnated fibrous material with absorbedalkaline liquor to stand to further react and soften the fibrousmaterial, and then subjecting the impregnated and softened fibrousmaterial to further mechanical after. standing to a second mechanicaldisintegrating treatment.

. 6. In the preparation of paper-forming stock from raw fibrousmaterial, the method which comprises mechanically disintegratingsubdivided quantity of caustic. liquor such that the liquor issubstantially all absorbed by the fibrous material during thedisintegration, allowing the disintegrated fibrous material and absorbedcaustic liquor to stand to permit further reaction and softening of thefibrous material; adding additional liquor to the material afterstanding to make down to a lower consistency, and then furthermechanically disintegrating the fibrous material at such lowerconsistency.

7. In the preparation of paper-forming stock from wood, the method whichcomprises sub dividing the wood into chips, adding controlled quantitiesof caustic liquor to the chips, rod milling the chips adm xed with thecaustic liquor to disintegrate the chips without cooking and causeimpregnation of the chips with the caustic liquor, and then subjectingthe impregnated ch'ps to further mechanical disintegrating treatment inthe presence of absorbed alkaline liquor to further disintegrate thechips and reduce the same to pulp. v

8. In the preparation of paper-forming stock from wood, the .methodwhich comprises subdividing Wood into chips, adding controlledquantities of caustic liquor to the chips, rod

milling the chips and admixed liquor to disintegrate the chips and causeabsorption of liquor by the chips, allowing the disintegrated chips withabsorbed caustic liquor to' stand to permit further reaction andsoftening of the disintegrated material, and then subjecting thedisintegrated material after standing to a second rod-milling treatment.

9. In the preparation of paper-forming stock from raw fibrous materialwhich has not previously been reduced to pulp, the method whichcomprises subdividing the raw fibrous material, mechanically-disintegrating by a pounding treatment of impact elements thesubdivided fibrous material in the presence of an alkal'ne liquorwithout cooking, and then mechanically refining the disintegratedfibrous material.

10. In the preparation of paper-forming stock from raw fibrous materialwhich has not previously been reduced to pulp, the method whichcomprises subdividing the raw fibrous material, rod milling thesubdividedfibrous material admixed with caustic liquor of substantialcausticity and at a controlled consistency to mechanically disintegratethe fibrous material without cooking, and then subjecting thedisintegrated fibrous material to a mechanical refining treat-,

jcomprises steeping the raw fibrous material in an alkaline liquor ofless than 10% strength under controlled conditions of temperature andz'pressureso as to soften the fibrous material Without substantialinjury to the fibers thereof,

' removing the steeped fibrous material from the steeping l'quor, aportion of the liquor of substantial alkalinity being retained in theremoved fibrous material, and then mechanically disintegrating theremoved fibrous material in the presence of the retained alkaline liquorby a pounding treatment of impact elements.

12. In the preparation of paper-forming stock from raw fibrous material,the method which comprises subdividing -;th raw fibrous material,

steeping the subdivided fibrous material in a caustic liquor maintained.at substantially atmospheric pressure and below the boiling point theremoved fibrous material in the presence of the retained caustic liquorand at a controlled consistency to mechanical disintegration by rodmilling.

13. Apparatus of the character described, comprising in combination,means for subdividing rawfibrous material, a rod mill, means forintroducing controlled and proportionate quantities of subdividedfibrous material and an alkaline liquor into said rod mill, a storagebin, and means for introducing the disintegrated fibrousmaterialdischarged from said rod mill into said storage bin, to permitthe disintegrated fibrous material with absorbed alkaline liquor tostand for further reaction and softening of the fibrous material.

14. Apparatus of the character described, comprising in combination,means for subdividing raw fibrous material, a rod mill, means forintroducing controlled and proportionate quantities of subdividedfibrous material and an alkaline liquor into said rod mill, a storagebin, means for introducing the disintegrated fibrous material dischargedfrom said rod mill into said storage bin, to permit the disintegratedfibrous material with absorbed alkaline liquor to stand for furtherreaction and softening of the fibrous material, a second rod mill, andmeans for introducing the disintegrated fibrous material after standinginto said second rod mill.

15. Apparatus of. the character described'comprising in combination,means for subdividing raw fibrous material, a rod mill, means forintroducing controlled and proportionate quantities of subdividedfibrous material and an alkaline liquor into said rod mill, a storagebin, means for introducing the disintegrated fibrous material dischargedfrom' said rod mill into said storage bin, to permit the disintegratedfibrous material with absorbed akaline liquor to stand for furtherreaction and softening of the fibrous material, a second rod mill, meansfor introducconsistency of the disintegrated fibrous material.

introduced into said second rod mill.

16. Apparatus of the character described, comprising in combination,means for subdividing raw fibrous material, a steeping tank having a Ifeeding end and a discharge end, means for introducing the subdividedfibrous material and caustic liquor into the feeding end of saidsteeping tank, means for moving the fibrous material through said tank,means for removing the steeped fibrous material from discharge end ofsaid steeping tank and for permitting draining of the same, whereby thesteepedfibrous material retains a controlled portion of the causticliquor still having substantial causticity, a rod -mill, and means forintroducing the fibrous material with retained caustic liquor havingsubstantialcausticity into said rod mill.

1'7. Apparatus of the character described, comprising in combination,means for subdividing.

fibrous material,. means for adding controlled quantities of alkalineliquor having substantial alkalinity thereto, a rod mill, means forintro-' .ducing the subdivided fibrous material and admixed alkalineliquor into said rod mill, a Jordan, and means for introducing thedisintegrated fibrous material into said Jordan.

18. In the preparation of paper-forming stock from wood, the method.which comprises subdi viding wood into chips, adding heated causticliquor to the chips in a proportion such that the liquor is capable ofbeing substantially all absorbed by the chips, rod milling the chips andadmixed caustic liquor to disintegrate the chips and cause absorption ofthe caustic liquor by the disintegrated chips, allowing thedisintegrated chips with absorbed caustic liquor to stand to permitfurther reaction and softening of the disintegrated chips, addingadditional liquor thereto to make down to a lower consistency, and thensubjecting this material at lower consistency to a second rod millingtreatment.

19. In the preparation of paper-forming stock from raw fibrous material,the method which comprises introducing the raw fibrous material beforeit is cooked or softened into a mechanical disintegrator in asubstantially dry state, subjecting the fibrous material when in. suchsubstantially dry state to a pounding treatment of impact elements toflatten and render the fibrous material more porous, then adding analkaline liquor to the treated fibrous material, and subjecting thefibrous material in the presence of the added alkaline liquor to adefibering treatment.

20. In the preparation of paper-forming stock from raw fibrous material,the method which comprises introducing the raw fibrous material beforeit is cooked or softened into a mechanical disintegrator in asubstantially dry state, sub-' jecting the fibrous material when in suchsubstantially dry state to a pounding treatment of impact elements toflatten and render the fibrous material more porous, then adding-analkaline liquor to the treated fibrous material, and then mechanicallydisintegrating the fibrous material by a" pounding treatment of impactelements in .the presence of the added alkaline liquor.

afresh supply of fibrous material being introduced into the mechanicaldisintegrator.

22. Inthe preparation of paper-forming stock from fibrous material, themethod which comprises mechanically disintegrating fibrous material inthe presence of a controlled quantity of alkaline liquor, addingadditionalliquor to the ,material after this-initial disintegratingtreatpounding treatment of is substantially all absorbed by the fibrousma- I terial during the rod milling treatment, allowing the rod milledchips with absorbed caustic liquor to stand to permit furthe' reactionand softening of the chips, adding a ditional liquor to the mass afterstanding to make down to. a lower consistency, then further rod millingthe mass at such lower consistency to effect disintegration of thechips, removing retained liquor from the disintegrated chips, andreturning removed liquor and adding it to subsequent chips to make downto the desired lower consistency for the second rod milling treatment.

24. A process of separating the fibers of fibrous vegetable material,which process comprises soaking the fibrous material in a cold causticalkali solution, and subjecting the soaked 26. In the preparation ofpaper forming stock from unpulped fibrous material, the method whichcomprises subjecting the unpulped fibrous material in the presence of achemical liquor and at a consistency in excess of 10% to mechanicaldeflbering by a pounding treatment of impact elements, then diluting thetreated material to a consistency below 10%, and subjecting the dilutedmaterial to a further pounding treatment of impact elements. 1

27. In the preparation of paper formingstock from raw wood chips, themethod which comprises subjecting the raw wood chips without coo tomechanicaldefibering by a pounding treatment of impact elements in thepresence of a chemical liquor and at a consistency in excess 'of 10% tocause impregnation of the chips by chemical liquor; then diluting theimpregnated chips to a consistency below 10%, and subjecting the dilutedmaterial in the presence of impregnating chemical liquor to a furtherpounding treatment of impact elements.

28. A process'of separating the fibers of fibrous material, whichcomprises soaking the fibrous material in a caustic alkali solution at atemperature below 100 C., and subjecting the soaked material tomechanical ,defibering by a impact elements without grinding.

JOHN 'I'RAQUAIR.

